Glossary

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The glossary provided here is largely based on “Seashells of Southern Florida: Bivalves,” by Paula M. Mikkelsen & Rüdiger Bieler, Princeton University Press. Production of this glossary was funded in part by the National Science Foundation’s Partnerships in Enhancing Expertise in Taxonomy [PEET] Program, NSF-DEB-9978119, “Bivalves - Research, Training, Electronic Dissemination of Data” (1999-2008) to Bieler and Mikkelsen.

O

OCELLUS (pl. OCELLI)
See EYE.
OPISTHODETIC
OPISTHODETIC fig.Type of dorsal LIGAMENT that occurs entirely on the posterior side of the UMBONES; see also AMPHIDETIC, PROSODETIC (figure: Periglypta listeri).
OPISTHOGYRATE/OPISTHOGYROUS
OPISTHOGYRATE/OPISTHOGYROUS fig.With the UMBONES curling posteriorly; see also PROSOGYRATE, ORTHOGYRATE.
OPISTHOPODIUM
Expanded heel on the FOOT of some bivalves (figure: Noetia ponderosa).
ORBITAL MUSCLES
Marginal adductor muscles spanning the fused ventral MANTLE folds, acting as accessory adductors; occurring in such families as Periplomatidae, Hiatellidae, and Trapezidae.
ORGAN OF DESHAYES
Collective term for the body of nitrogen-fixing, CELLULASE-producing bacteria in the gills of Teredinidae; ducts in the afferent branchial vessels empty into the esophagus; also called Gland of Deshayes.
ORGANS OF WILL
Pigmented glandular structures of unknown function on the middle and inner MANTLE folds of Pinnidae; they have been shown not to be eyespots, and are possibly associated with production of pigment rays on the shell.
ORNAMENT
See SCULPTURE.
ORTHOGYRATE/ORTHOGYROUS
ORTHOGYRATE/ORTHOGYROUS fig.Having the UMBONES curling directly toward one another or ventralward; see also PROSOGYRATE, OPISTHOGYRATE (figure: Tucetona pectinata).
OSCICULUM
See LITHODESMA.
OSCULUM (PL. OSCULA)
See SEPTIBRANCH.
OSSICLE, CALCAREOUS
See LITHODESMA.
OSTIUM (pl. OSTIA)
An opening in (1) the ctenidia, created by the intersection of filaments and interfilamental junctions, or (2) the septum, containing gill filaments; see also EULAMELLIBRANCH, SEPTIBRANCH.
OTOCYST
See STATOCYST.